The solar energy incident upon the roof of a low-rise building in most of the United States is sufficient during the winter months to provide heating for the building and is more than sufficient during the summer months to power a cooling unit to maintain comfort. To utilize this energy requires that the sunshine be absorbed and converted to heat and that the heat be collected and stored for use during periods when the sun is not shining, as at night and during very cloudy weather.
Many methods for heat collection and storage have been proposed heretofore. Some of these methods utilize passive systems such as roof ponds which are suitable in low dew point, non-freezing climates. Other methods utilize air-cooled collectors and rock bin heat storage. Another system heretofore proposed employs a liquid cooled collector and a tank of water for heat storage.
The major impediment to widespread adoption of the liquid cooled collector type of solar heating and cooling in the U.S. is economic. Inexpensive, strong and durable materials must be used. Heretofore copper and aluminum have been employed. However these materials are too expensive and structurally weak. Other prior art devices have not been suitable for assembly line mass production and its attendant economics. Copper, aluminum and plastics have heretofore been employed in solar collectors. While some of these materials avoid corrosion problems they are relatively expensive and structurally weak, requiring reinforcement of the roof structure to accommodate collectors employing these materials.